Manufacture of artificial products



V Patented Dec. 29, 1936 UNITED STTES ATENT OFFICE William Ivan Taylor, Spondon, near Derby, England, assignor t Oelanese Corporation, a corporation of Delaware No Drawing. Application January 9, 1933, Serial 4 Claims.

This invention relates to the manufacture of artificial filaments, threads, yarns, and the like, and is more particularly applicable to the production of such products from solutions of cellulose acetate or other cellulose esters or ethers.

It is well known that in the early days of the manufacture of cellulose acetate artificial sill; considerable difiiculty arose from the fact that the filaments produced had a relatively fiat cross-section and exhibited the disadvantage of scintillation when in fabric form. These difliculties were overcome to a large extent by the use of spinning solutions containing upwards of 20%, and particularly 25% or more, of cellulose acetate, such process being patented in U. S. Patent No. 1,688,351 of Dr. Henry Dreyfus.

In British Patent No. 385,617 processes are described wherein the cross-section of filaments or the like is improved by incorporating in the spinning solution substances which have the effect of increasing the viscosity of the said solution, so that bulbous filaments may be produced without having recourse to concentrations of cellulose acetate of 25% or more, or so that the filaments produced from solutions of a concentration of 25% or more are still further improved in cross-section. A similar object is achieved by the invention described in British Patent No. 388,400 in which there is incorporated in the spinning solution a substance, preferably a nonsolvent for the base of the spinning solution, which is more volatile than the main solvent of the spinning solution, for example diethyl ether in the case of acetone solutions of cellulose acetate.

The present invention is also concerned with methods for controlling the cross-section of the filaments. According to the present invention there is incorporated in the spinning solution a substance or substances which are not removed from the filaments during the formation of the materials, and which have the effect of increasing the total amount of substance in the filaments after their formation, or in other words decreasing the proportion of solvent relative to filament forming substances without increasing the proportion of cellulose or cellulose derivative therein. In the case of spinning the solutions by dry spinning methods, to which, in view of the difiiculties referred to above, the present invention is mainly applicable, the added substances will be relatively non-volatile, so that they are not removed during the spinning operation, or at least during the early stages thereof when the final form of the spun products is being determined. Similarly in In Great Britain January 18,

wet spinning operations the substance should be insoluble in the coagulating bath, or at least insufficiently soluble to be removed therefrom during the main part of the coagulation, or during theearly stages thereof, when the filaments or other products are receiving their form.

The invention may be applied to the production of bulbous filaments or like products of improved cross-section from any suitable spinning solutions, including viscose, cuprammonium and nitro-cellulose solutions, but is more particularly applicable to the case of cellulose acetate or other organic esters or ethers of cellulose, in the dry-spinning of which fiat cross-sections more frequently occur, and the invention will be more particularly described in relation to the dry spinning of solutions of cellulose acetate.

Preferably the substance added to the spinning solution for the purpose of improving the crosssection is sufiiciently soluble in the solvent of the spinning solution to enable it to be dissolved in substantial proportions, and is insufficiently compatible with the cellulose acetate or other base of the spinning solution to materially retard subsequent removal of the added substance from the formed filament or other products, where such removal is desired. Furthermore the added substance is preferably easily soluble in water or other common solvent sothat removal after filament formation is facilitated.

In spinning organic solutions of cellulose derivatives we find that organic substances or mixed inorganic-organic substances are most suitable, since they are most soluble in the organic solvents employed in the spinning solution. At the same time it is most convenient that the added substances should be soluble in water, firstly because it is most convenient to remove them after filament formation by means of water or aqueous washing liquids, and secondly because water solubility is generally associated with a large class of bodies which are relatively incompatible with the cellulose acetate or other cellulose derivative. For this reason it is convenient to employ, in the case of dry spinning solutions of cellulose derivatives in volatile organic solvents, bodies which contain hydroxy groups, preferably alcoholic in character, and/or carboxy groups.

As examples of suitable substances which may be added, we may instance the aliphatic hydroxy acids, for example malic acid, citric acid, mandelic acid, tartaric acid, and tartronic acid; aliphatic di-carboxylic acids, for example axalic acid, malonic acid, succinic acid and glutaric acid; ali- K in general necessary to use relatively large prophatic and aromatic amino acids, for example glycine, alanine, valine, tyrosine, and phenyl glycine; aromatic acids such as benzoic acid and. salicylic acid, and also the salts of such acids, for example sodium oxalate, sodium benzoate and sodium salicylate. Other substances which may be used according to the process of this invention are the sugars, for example levulose, maltose, dextrose, sucrose, and dextrin, or derivatives thereof, e. g. the acetates, benzoates and compounds With aldehydes and similar substances. Although as stated above water-soluble substances are preferably employed, the use of water-insoluble substances, e. g. naphthalene, anthracene and other hydrocarbons is not excluded. Such substances are however preferably soluble in a solvent which is a non-solvent for the base of the spinning solution, so that they may be easily removed from the formed materials.

The invention also contemplates the use of inorganic substances which are soluble in the solvents of the spinning solutions, and preferably also in water, e. g. ammonium bromide, ammonium nitrate, calcium nitrate, potassium bromide, potassium iodide, magnesium bromide, and zinc chloride.

We have also discovered that the nature of the cross sections of the filaments may be controlled by the incorporation of liquids, and preferably relatively non-volatile liquids into the spinning solutions. Thus, forexample, such substances as glycol monoacetate, glycol diacetate, diethylene glycol monoacetate, di-, tri-, and tetra-ethylene glycols, the ethyl or other ethers of di, tri-, and tetra-ethylene glycols, glycerol and other polyhydroxy alcohols and their ethers, esters and ether-esters, acetophenone, benzyl butyrate, and vegetable or other oils may be employed.

In the case of using liquids, however, and particularly in the case of solvent liquids, it is found portions in order to obtain filaments of improved or more bulbous cross-section. In fact, up to a certain point, e. g. up to 50-70% in the case of glycol monoacetate with cellulose acetate, an acthe cross-section of the products.

The foregoing bodies may also be added to spinning solutions of organic derivatives of cellulose dissolved in organic solvents for wet spinning purposes, provided that coagulating baths are used which do not dissolve the said bodies or which dissolve them only to a limited extent. Thus, for instance, many of the above bodies may be used in conjunction with hydrocarbon coagulating baths, or baths containing most of the vegetable or animal oils.

A relatively small addition of solid substance to the spinning solution produces substantially improved cross-section. For example an addition of 4% of citric acid, calculated on the weight of the cellulose acetate or other cellulose derivative, produces substantially improved cross-sections as compared with a spinning solution of the same concentration of cellulose derivative not containing the citric acid. An addition of 8% calculated on the weight of the cellulose acetate produces a still further substantial improvement, while the maximum improvement appears to be obtainable by means of an addition of 16 to 20%, or even up to 30%, of the citric acid based on the weight of the cellulose derivative. By the addition of the citric acid or other agent the concentration of cellulose acetate in the spinning solution so as to produce substantially round filaments may be reduced below 25% and to 20% or even less. We find it most convenient to employ a concentration of 20 to 23% and to add citric acid or the like in such a proportion that the total solids contained in the spinning solution represent a proportion of the spinning solution of about 25 to 30 or 40%.

In the case of using liquids however, and particularly solvent liquids, it is, as stated, in general necessary to use relatively high proportions of liquid based on the weight of the cellulose derivative e. g. 50-70 or more, preferably--90 or or more, in the case of solvent liquids, in the production of bulbous filaments. When non-solvent liquids are employed, however, smallor proportions may give satisfactory results.

The ability to obtain bulbous cross-sections by the addition of certain substances as described above is of great value, particularly in dry spinning operations, since it enables the spinning to be conducted under the modern high spinning speeds of 200 to 300 or 400 metres per minute, and at the same time enables the drawdown of the filaments to relatively low deniers to remain unimpaired, whereas with spinning solutions of 25 to 30% strength the draw-down obtainable is appreciably diminished by increasing the spinning speed from 100 to 200 metres or more per minute. It appears in fact as if the draw-down were a function of the concentration of cellulose derivative in the spinning solution and of the spinning speed, and by enabling the concentration of cellulose derivative to be reduced without the disadvantage of producing flat or scintillating filaments the process of the present invention is capable of producing very low filament deniers at high speed. The invention is however not limited to the use of high spinning speeds and is not limited to any particular concentration of cellulose derivative, since as already indicated the addition of citric acid or other substances as described above considerably improves the roundness of the cross-section. In order still further to facilitate the draw-down of the filaments to low deniers it is desirable to add to a spinning solution containing water-miscible solvents a proportion of water which apparently much improves the'capacity of the filaments to draw out. Thus, for instance, water may be added in a proportion of 3 to 5% or even up to 10% of the solvent mixture.

The following examples are given in order; to illustrate the invention and are not to be regarded as in any way limiting it.

7 Example 1 Acetone-soluble cellulose acetate is dissolved in a solvent mixture comprising 94% acetone and 6% of water to .make a. 23% solution therein. To this is added an amount of citric acid equal to 20% of the cellulose acetate. employed. This solution is spun through jets of 0.055 millimetre diameter into an evaporative medium at a spinning speed of l80200 metres per minute. The products are then washed, e. g. with water, to remove the citric acid. The filamentsobtained exhibit a good bulbous cross-section.

Example 2 An aqueous acetone solution of cellulose acetate of 23% concentration, which contains cane sugar in amount equal to 20% of the cellulose acetate in the solution is spun under similar conditions to those obtaining in Example 1. The resulting filaments are treated with an aqueous bath to dissolve out the cane sugar, and products having a good cross-section and low denier may be obtained.

Example 3 Sufficient calcium nitrate is added to a 23% solution of cellulose acetate to make the total concentration of solids in the solution equal to 25 to 28% of the solution, and the solution is then spun under similar conditions to those obtaining in Example 1. The calcium nitrate is then washed out by means of an aqueous bath, and the resulting filaments exhibit a good bulbous cross-section.

Example 4 Acetone-soluble cellulose acetate is dissolved in a solvent mixture comprising 94% acetone, and 6% water to make a 23% solution therein. To this is added glycol monoacetate in amount equal to of the cellulose acetate employed, and the solution is then spun under the conditions set out in Example 1. The glycol monoacetate is subsequently dissolved out of the filaments and the resulting filaments have a good bulbous cross-section.

The production of filaments of a more bulbous cross-section may be still further assisted by the addition to the spinning solution of highly volatile bodies, such as the ethers, or of substances which increase the viscosity of the spinning solution or by the use of cellulose esters or ethers of high viscosity characteristics, as described in British Patents Nos. 385,617 and 388,- 400, thus enabling the cellulose derivative to be used in still lower concentrations and/or enabling greater draw-down or greater roundness of cross-section to be obtained. In addition the roundness of the products may be improved by blowing or drawing air or other gas across the filaments in the early stages of their formation, and it is, in general, advantageous to promote a rapid evaporation of the solvent in the early stages of spinning. Thus as described in U. S. Patent No. 1,934,618 additional evaporative medium may be introduced in the Vicinity of the nozzle, and/or collector devices such as are described in U. S. Patents Nos. 1,814, l68, 1,942,540 and 1,933,587, may be employed.

As already indicated the invention is most important in relation to the spinning of solutions of cellulose acetate or other cellulose esters or ethers, for example cellulose formate, propionate, butyrate, nitro-acetate, or methyl, ethyl or benzyl celluloses, and cellulose ether-esters e. g. ethyl cellulose acetate and oxyethyl cellulose acetate. However, similar results may be achieved by the addition of suitable compounds to viscose, cuprammonium, nitro-cellulose or other spinning solutions.

What I claim and desire to secure by Letters Patent is:-

1. Process for the manufacture of bulbous artificial filaments, which comprises spinning in an evaporative atmosphere a solution of an organic derivative of cellulose and an aliphatic hydroxyacid which is incompatible with said organic derivative of cellulose, which is solid at the spinning temperature and which separates from the solution in crystalline form, the proportion of organic derivative of cellulose being at most 23% by Weight of the solution and the total solid content being at least 25% by weight of the solution.

2. Process for the manufacture of artificial filaments, comprising extruding a solution of an organic derivative of cellulose containing citric acid in a proportion of 16 to 30% of the weight of the organic derivative of cellulose, said solution having a total solid content amounting to more than 25% by weight of the solution, into an evaporative atmosphere such that a substantial proportion of the said acid remains in the formed filaments.

3. Process for the manufacture of artificial filaments, comprising extruding a solution of cellulose acetate containing citric acid in a proportion of 16 to 30% of the weight of the cellulose acetate, said solution having a total solid content amounting to more than 25% by weight of the solution, into an. evaporative atmlosphere such that a substantial proportion of the said acid remains in the formed filaments.

4. Process for the manufacture of artificial filaments, comprising extruding a solution containing approximately 23% by weight of cellulose acetate and a quantity of citric acid amounting to approximately 20% of the weight of the cellulose acetate into an evaporative atmosphere such that a substantial proportion of the citric acid remains in the formed filaments, and subsequently removing the citric acid by Washing with an aqueous medium.

WILLIAM IVAN TAYLOR.

CERTIFICATE OF CORRECTION.

Patent No. 2,065,766. December 29, 1936.

WILLIAM IVAN TAYLOR.

It is hereby certified that the name of the assignee in the above numbered patent was erroneously described and specified as "Celanese Corporation" whereas said name should have been described and specified as Celenese Corporation of America, a corporation of Delaware, as shown by the records of assignments in this office; and page 1 second column, line 54, for "axalic" read oxalic; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of March, A. D. 1937.

Henry Van Arsdale (Seal) Acting Commissioner of Patents. 

